The studies proposed in this application represent a request to continue characterizing naturally-occurring gene variation that determines seizure susceptibility in mice. The primary model under study involves two common strains of inbred mice that differ robustly with respect to their susceptibility to experimentally-induced seizures, C57BL/6J (B6), which is relatively seizure resistant, and DBA/2J (D2), which is relatively seizure susceptible. Whereas the short term goal of studies in this project is related to the identification of seizure susceptibility genes in mice, the long term goal involves translation of these studies into focused hypotheses and studies involving human patients with epilepsy. Thus, in the past funding period, we used the B6-D2 mouse model to identify Kcnj10 as a putative seizure susceptibility gene underlying the quantitative trait locus (QTL) on distal Chr 1. Upon translation to a clinical study, we showed that KCNJ10 genetic variation in humans is associated with risk for common forms of epilepsy. Importantly, this latter finding was confirmed by an independent laboratory and exists as one of the few replicated epilepsy genetic associations in the literature. Thus the past funding period enabled us to demonstrate proof of principle and the overall utility of our translational research strategy. As a result of the success achieved in the dissection and translation of the distal Chr 1 QTL (Szs1) in the B6- D2 model, we have recently (February 2008) submitted a new grant application to study the mechanism of Kcnj10 genetic variation in seizure susceptibility and thus do not propose further study of that gene in this project. Rather, we will focus on analysis of seizure susceptibility QTLs of next highest priority in the B6-D2 model which were also studied in the previous funding period. Thus in Aims 1 and 2 we propose to fine-map and analyze candidate genes in critical QTL intervals on Chr 5 and Chr 15, respectively. This work will include creation of recombinant congenic strains between B6 and D2 mice, determination of seizure susceptibility using well-established paradigms involving maximal electroshock seizure threshold (MEST) and chemical convulsants, bioinformatics and mRNA and protein analysis of candidate genes. Aim 3 will focus on a new genetic model developed in the last funding period involving C57BL/KsJ (Ks) and C57BL/10SnJ (B10S) inbred strains of mice. In this model, we propose to confirm MEST QTLs identified on Chrs 3, 4, 6 and 8 by capturing them in congenic strains which will be created rapidly and in parallel with each other. The extent of the influence of MEST QTLs on seizure susceptibility will be evaluated in those congenic strains in which MEST QTLs are captured by testing them with chemoconvulsants pentylenetetrazol (PTZ), kainic acid (KA) and pilocarpine (PC). QTLs will be prioritized for further dissection based upon the results from all paradigms. The studies proposed in this project will have immediate impact on the field of epilepsy genetics research. Since our laboratory is dedicated to a translational research strategy, results will be used directly to inform clinical studies of patients with epilepsy. We maintain a growing repository of over 1000 DNA samples from patients with epilepsy and use them to investigate candidate genes that are suggested by the mouse studies. Work completed in this project during the past funding period provides proof of principle for the utility of this strategy and thus serves as a prototype that we propose to follow for further elucidation of the complex genetic architecture that defines human epilepsy. Ultimately, a better understanding of the biological basis of seizure susceptibility and genetic predisposition to epilepsy will facilitate the development of novel and more effective therapeutic options for patients and may one day lead to a cure for this devastating group of diseases. PUBLIC HEALTH RELEVANCE: This project involves the identification of genes in mice that determine their susceptibility to experimentally- induced seizures. Whereas the short term goal of the project involves the identification of seizure susceptibility genes, the longer term goal is to try to understand how they influence seizure susceptibility. Ultimately, the knowledge gained from these studies on mice will be applied in our laboratory to human patients with epilepsy and thus will have immediate impact on the field of epilepsy genetics research. Since our laboratory is dedicated to a translational research strategy, results from work on mice will be used directly to inform clinical studies. We maintain a repository of over 1000 DNA samples from patients with common forms of epilepsy and we use them to investigate genes that are suggested by our mouse research such as those proposed in this project. Ultimately, a better understanding of the biological basis of seizure susceptibility in mice and genetic predisposition to epilepsy in humans will facilitate the development of novel and more effective therapeutic options for patients with epilepsy and may one day lead to a cure for this devastating group of brain diseases.